Conventional mid-infrared focal plane arrays are based on the use of mercury-cadmium-telluride (HgCdTe) photodetectors. Alternatives to HgCdTe photodetectors are being developed which promise operation at higher temperatures and a detectivity comparable to or better than the HgCdTe photodetectors. Among these alternatives are photodetectors formed from antimonide-based type-II superlattices in which there is, at least theoretically, a promise of longer intrinsic carrier lifetimes due to the suppression of Auger recombination. Additionally, the antimonide-based type-II superlattices have a staggered band alignment which allows both the energy band structure and the energy bandgap of the superlattice to be tailored to enhance detector performance for the absorption of infrared light over a wide wavelength range of about 3 to 25 microns (μm) or more. The development of infrared focal plane arrays including devices using antimonide-based type-II superlattice photodetectors has been reviewed in an article by A. Rogalski entitled “Competitive Technologies for Third Generation Infrared Photon Detectors” in Proceedings of the Society of Photo-Optical Instrumentation Engineers (SPIE), vol. 6206, 62060S (2006). Another review of type-II superlattice photodetectors can be found in an article by G. J. Brown entitled “Type-II InAs/GaInSb Superlattices for Infrared Detection: an Overview” in Proceedings of the Society of Photo-Optical Instrumentation Engineers (SPIE), vol. 5783, pp. 65-77 (2005).
The present invention provides an advance over the art in the development of antimonide-based type-II superlattice photodetectors by providing a substantially planar geometry for a two-dimensional (2-D) array of photodetectors with a plurality of III-V compound semiconductor layers therein being contiguous (i.e. connecting without a break) across all of the photodetector elements in the 2-D array.
The substantially planar geometry of the infrared focal plane array photodetector of the present invention eliminates a need for etching a mesa structure about each photodetector element which is prevalent in the prior art, and also avoids edge surface recombination which occurs at sidewalls of each photodetector element in the prior art etched mesa structure where the superlattice and a semiconductor junction therein are exposed.
Additionally, the infrared focal plane array photodetector of the present invention avoids a need for epitaxial re-growth which is complicated and time consuming, and which requires careful attention to detail to remove any surface oxide'prior to the re-growth.
These and other advantages of the present invention will become evident to those skilled in the art.